Disposable diapers are generally well known in the art and are becoming increasingly acceptable in the marketplace as a sanitary protection item, especially for use in infant and child care to absorb urine and fecal discharges. Unitary, preshaped or prefolded diapers which are generally comprised of a porous facing layer, a fluid impervious backing sheet and a highly absorbent batt sandwiched therebetween, which require no supplementary holders or panties, and which may be disposed of after a single use, have proved to be especially popular. Even though such diapers are growing in popularity, one feature which still appears to need improvement is obtaining a better, more satisfactory, fit. In discussing the problem of fit with mothers it was found that, while they wanted a diaper which neatly conformed to the child with a minimum of bulk and a maximum of comfort, what would really be more desirable to them than an aesthetically neat fit would be a diaper which minimized leakage both at the waist and at the crotch or thigh area.
Commercially successful attempts to improve fit in the past have involved geometrical folding of rectangular diapers for the purpose of narrowing the apparent width in the crotch area to facilitate application to the child. Typical examples of two variations of such prior art folds may be found in U.S. Pat. No. Re 26,151 to Duncan et al in which a rectangular diaper is provided with parallel longitudinal folded box pleats and a loose overlying flap along each side, and in U.S. Pat. No. 3,196,874 to Hrubecky in which a rectangular diaper is provided with triangular-shaped infolds in the crotch area. While these prefolded constructions permit the diaper to be more easily applied to the child, some disadvantages remain with respect to eliminating or minimizing leaks during use. First, when these prefolded rectangular diapers are used there is excess bulk between the legs which may cause discomfort; second, the folds of these rectangular diapers are generally linear and the relatively non-conformable structure of disposable diapers prevents a closely conforming fit at the buttocks or thighs, often leaving undesirable gaps in those two areas which permit leaks to occur; and third, when applied to the child the non-conforming sides of the rectangular diaper tends to pull the waist down at the sides and thereby cause the diaper to gap at the front of the waist where leaks can then occur.
Attempts to reduce bulk between the legs such as by reducing the width of the absorbent pad in the crotch area have also been tried, but again, because the materials used in constructing disposable diapers are relatively non-conformable, a close fit at the thigh is difficult to achieve and undesirable gaps still occur. In addition, the reduced width of the absorbent pad component cuts down on the available absorbent capacity in the crotch area which is another cause of leakage because of an inability of the reduced amount of material to adequately absorb urine in an area of the diaper where good absorbent capacity is most needed. One suggestion for eliminating such gaps at the narrowed crotch area was to provide the diaper edges with elasticized thin flexible flaps at least three-fourth inch in width when measured from the elasticized line to the edge of the absorbent pad in the crotch area as described in U.S. Pat. No. 3,860,003 to Buell. While this modification apparently provides a seal at the thighs because the tensioned elastic presses the easily deformable flap into close contact with the legs, mothers who tested diapers made in accordance with the structure described in the patent expressed several objections. First, they found that discharged fluids collected near the diaper edges and sometimes permeated into the interface between the flap and the skin where it could cause skin irritation aggravated by the tight fit of the elastic holding the flap against the skin; second, because it was necessary to reduce the width of the pad in the crotch area in order to provide the required flap width, the smaller amount of absorbent material available appeared to become excessively wet in use and, even though the elastic present in the flaps seemed to provide a tight seal at the leg, some leaks still occurred; and third, when the reduced width pad did become excessively wetted it tended to bunch up or disintegrate and hinder fluid transfer to other unused parts of the pad.
An older U.S. Pat. No. 2,273,542 to Tasker relating to disposable diapers suggests that a rectangular diaper can be made to fit better around the legs by elasticizing the entire length of the side edges so they are stretchable in an endwise direction. In this structure, the elastic provides transverse wrinkles in the full width of the diaper and when such a diaper is applied to a child it is stated that these wrinkles will open to form a sack in the crotch area. While this may be true, the full rectangular configuration of the diaper still leaves excessive bulk and width between the thighs, and leg action then tends to pull the diaper down and cause gaps at the waist. The full length elastic also makes fastening at the sides of the waist less convenient.
This invention is directed to an improved disposable diaper, in which the absorbent batt in the crotch area is of decreased width as compared to the waist to provide less bulk in the transverse direction. The diaper is elasticized only along the edges in the narrowed crotch area in a manner to give a more conformable leg fit as well as improved functional absorbent capacity. Attaching the elastic immediately adjacent to the batt edges and also bonding the batt surface to the backing or facing in that area to unitize the structure forces the batt to contract as the elastic contracts thereby longitudinally condensing the batt and producing gross transverse rugosities in the crotch area whereby an increase in the effective absorbent capacity of the batt in that area is also obtained. Limiting the elasticized edges to the narrowed crotch area foreshortens and provides transverse rugosities in the diaper batt only in the crotch area while minimizing the development of gaps at the waist.